alsancle

Why do Valves Stick?

Recommended Posts

So I have an issue and I'm confused how it happened.   I've got 4 stuck valves on an overhead valve straight 8.   Here are the details:

 

1. Engine was done 25-30 years ago before I bought the car.  

 

2. I would start car every 3/4 months and let it run to warm.  I've done this for the last 14 years.

 

3. Car is stored in a basement garage,  temp stays between 60-70 year round.  This is not feel like a humid or moist environment but now I'm wondering so will get a humidity gauge.

 

4. I missed a start cycle and went 6 months and the car wouldn't start.  A compression test showed no compression and we found the stuck valves.

 

5. With the valve cover off, there is plenty of oil in the head but the valves are really stuck hard.

 

6. I run 30 weight Valvoline racing oil.  Only racing or aviation gas in the tank.  It has never had pump gas since I've owned it.

 

I'm totally confused as to how this happened.  I understand in a car that sits for a long time, but is 6 months really that long?

Share this post


Link to post
Share on other sites

A friend of mine has a 1958 Chevy 6 cyl. 1/2 ton PU. He started it after sitting for 4 months, heard a noise and the truck ran poorly. It turned out he had 2 broken rocker arms on 2 intake valves. the cause was a scummy build up on the valve stem. He has added Marvel Mystery Oil to the fuel tank and has not had a problem since.   

Share this post


Link to post
Share on other sites

Old gas probably caused it, and unfortunately these days, old gas can be 6 months.  And, from your description, you weren't adding new gas, just starting it every now and then.

 

I learned the same lesson with a Lincoln that hadn't been run for a while.  The gas had evaporated, and even with fresh gas in the tank, a problem occurred.  I started the car, it ran fine, even drove it around some, got it up to operating temperature.  The next day, it wouldn't start at all.  After a lot of headscratching and cussing, we found out the valves were stuck and pushrods bent like pretzels.  And when I say stuck, I mean STUCK!  Had to drive them out with a punch and hammer.

 

The old gas gummed up the stems, big time.

 

One day I had a friend call me, he had two Pontiacs that had been sitting for not quite two years.  He'd started them  a couple of times.  He went to start them again, and they wouldn't start.  I told him to drop the gas tanks and clean them out, he looked at me like I was crazy.  A couple of weeks went by, he called, "How'd you know it was bad gas, it wasn't that old?"  He'd cleaned the tanks and fuel system and all was well.

 

Ethanol gas can go bad in 6 months.  Regular, non-ethanol modern gas MIGHT last two years, but probably not....

Share this post


Link to post
Share on other sites

I hear you on the gas but this is AV gas, which I thought never went bad.  Maybe eventually it does.  This gas was probably a few years old.

Share this post


Link to post
Share on other sites

A couple days of penetrating oil and they freed up.  Will drain the AV gas and I guess make sure I run through the tank more often.  I'm still really surprised.

Share this post


Link to post
Share on other sites

I don't know if it's an old wives tale but I put Premium (91 octane) fuel in my older cars that I don't drive as often. The thought is the higher octane fuel is less volatile and lasts longer.

 

Share this post


Link to post
Share on other sites

When an engine sits, moisture, just due to humidity, accumulates in the crankcase and rocker cover. That moisture can condense in the valve stems and guides and cause to rust and often cause sticking. Especially true on a rebuilt engine where valve stem clearance is still close.

That is how the oil in an engine not running for a long time can gunk up.

 

Even though you do run the engine once in a while - the moisture still can build up.

Share this post


Link to post
Share on other sites

I often wonder if the old time fix of reviving worn out valve guides via the "knurling" method helps to reduce stuck valves. Kind of makes sense as the oil is more apt to be trapped into the knurled grooves.

I am contemplating doing that to my spare Packard inline six engine. Would that warrant a new topic for discussion?

Comments?

Share this post


Link to post
Share on other sites

I would be interested in opinions on the knurling also.

 

After freeing the valves over 3 days we were able to get it running again.  I'm thankful there were no bent valves. 

Share this post


Link to post
Share on other sites

It is my understanding higher octane fuel has more aromatic components which evaporate faster than components in lower octane fuels, thus reducing the octane rating of the fuel.

 

Starting an engine and idling it for a short while is a sure way to fill it with condensation. Even if run 'til the temp gauge comes to normal, the engine doesn't really reach operating temperature everywhere and evaporate all the water vapour inside it. The muffler will fill with water too.

 

Mine has sticky valves because of a carbon build-up at the top of the stems. Do any of those "carbon burning" products actually work?

  • Like 2

Share this post


Link to post
Share on other sites
On ‎9‎/‎15‎/‎2016 at 0:01 AM, Spinneyhill said:

It is my understanding higher octane fuel has more aromatic components which evaporate faster than components in lower octane fuels, thus reducing the octane rating of the fuel.

 

Starting an engine and idling it for a short while is a sure way to fill it with condensation. Even if run 'til the temp gauge comes to normal, the engine doesn't really reach operating temperature everywhere and evaporate all the water vapour inside it. The muffler will fill with water too.

 

Mine has sticky valves because of a carbon build-up at the top of the stems. Do any of those "carbon burning" products actually work?

 

I agree that just starting the vehicle for a little bit and then turning it off causes condensation issues.  I know persons that start their cars  every month all winter and let them run for a few minutes.  I think that is a bad practice.

 

When I put any vehicle away for the season, I always change the oil, take it out for a good drive, fill it up with gas and then park it.  I do not start it until spring when I am going to get it out for the season.  I have never had any issues with sticking valves, etc.

Share this post


Link to post
Share on other sites
On 15/09/2016 at 11:16 AM, tom_in_nh said:

I often wonder if the old time fix of reviving worn out valve guides via the "knurling" method helps to reduce stuck valves. Kind of makes sense as the oil is more apt to be trapped into the knurled grooves.

 

I would imagine the rough knurled surface would be very good at grinding away inside the end of the valve guide. It would be a fiddle getting the knurling just deep enough that the material pushed up still fits into the valve guide. It would also be a fiddle on a hardened valve stem, so one doesn't bend it. No, fix the problem, don't add another.

 

Or are you proposing the tighten the valve guides by knurling the outside? Then you will be removing block material when you push it back in, making it harder when new guides are fitted. Nup, to much "bush mechanic" stuff for me.

Edited by Spinneyhill (see edit history)

Share this post


Link to post
Share on other sites
1 hour ago, Spinneyhill said:

I would imagine the rough knurled surface would be very good at grinding away inside the end of the valve guide. It would be a fiddle getting the knurling just deep enough that the material pushed up still fits into the valve guide. It would also be a fiddle on a hardened valve stem, so one doesn't bend it. No, fix the problem, don't add another.

Spinneyhill, what are you talking about?

Reading your post, it comes across to me that you believe that the outside diameter of the valve gets knurled. Is that what you are conveying?

If so, that is not what you do. The inside diameter of the valve guide gets knurled, followed up by the burnishing / reaming to size. 

Pretty common procedure back in the day....

Share this post


Link to post
Share on other sites

Spinneyhill, 

I see that you have edited your post to include the knurling of the outside diameter of the valve guides.

I now know for sure that you are not familiar about this knurling procedure.

Please stop with your opinions on this matter, your lack of knowledge on this subject is sticking out like a sore thumb. Trying to be graceful about this, to spare you further embarrassment.

 

Share this post


Link to post
Share on other sites

The issue of sticking valves has been around forever. That is how "Marvel Mystery Oil" came about.

It is very unlikely that modern fuels are an issue - I think it is a red herring.

Share this post


Link to post
Share on other sites
4 hours ago, tom_in_nh said:

Spinneyhill, 

I see that you have edited your post to include the knurling of the outside diameter of the valve guides.

I now know for sure that you are not familiar about this knurling procedure.

Please stop with your opinions on this matter, your lack of knowledge on this subject is sticking out like a sore thumb. Trying to be graceful about this, to spare you further embarrassment.

 

 

tom_in_nh, thanks for the graceful education. Clearly I am ignorant. I only ask you to educate me. I didn't know (or imagine) you could knurl inside a valve guide. Sorry I am the only one stupid enough to say something. What sort of tool do you use?

 

Maybe I should have asked what on earth you are talking about - I am a Geotechnical Engineer, not a machinist or motor mechanic or anything else familiar with motor repair techniques, other than my own bumbling attempts to keep a 1930 vehicle going and in good repair. Everyone is entitled to an opinion, even the ill-informed.

Share this post


Link to post
Share on other sites

OK, now we can move on.

In a nutshell, the tool used to do the major operation of the valve guide knurling acts like a thread roll tap. It merely displaces metal in order to close up the bore of the worn out valve guide.

You then use another tool to bring the size of the bore back into tolerance, so the valve can fit.

The resulting repair has perhaps 30 - 40 spiral grooves in which oil can fill inside. Thus the long term lubrication, instead of the potential of a dry bore prone to rusting up. Capisce, yet?

There are folks that will say this is a half assed repair, instead of guide replacement. It is a cheap and fast method that was common back in it's day. 

Obviously there is a limit on how worn the guides should be in order for this fix to be successful. It is simply another alternative that could help with valves rusting up over time.

Hope this helps.

 

Share this post


Link to post
Share on other sites

When I had the cylinder head rebuilt for my 1933 Chevrolet Master back around 1976, the machine shop knurled the valve guides and installed the NOS Chevrolet valves I provided.

 

The rebuild was done by a shop that specialized in farm tractors.  The gentleman doing the rebuild had worked in the same shop for over 40 years and said he thought knurled guides were better than un-knurled new guide for the oil lubricating reason mentioned by Tom, as long as the guides did not have excessive wear.

 

I reinstalled the head and the engine has been running great for the past 40 years.

 

 

Edited by Vila (see edit history)

Share this post


Link to post
Share on other sites
19 hours ago, DonMicheletti said:

The issue of sticking valves has been around forever. That is how "Marvel Mystery Oil" came about.

It is very unlikely that modern fuels are an issue - I think it is a red herring.

It's not the new gas that's the issue, it's gas that's been sitting in a tank for a couple of years.  In other words, it's "aged" new gas, and there's no red herring about it, it will go bad, your car may not start, the fuel tank will get deposits in it, and in some instances it will cause damage to the engine.

 

I don't know how to make you believe that if you haven't seen it, but in the last ten years, I've seen numerous issues with "new" aged gas, or "aged" new gas, however you want to say it......

Share this post


Link to post
Share on other sites

I agree pump gas will gum everything up in short order but this car has never had pump gas in it while I have owned it.  Either Cam-2 or AV.  I'm wondering if the high octane AV gas does not have enough lubricants and does evaporate quickly.  I do not think it was moisture but maybe it was.

Share this post


Link to post
Share on other sites

I have read around a bit. Sticking valves are apparently caused by a buildup of carbon and that occurs because the valve guide and valve stem are worn, allowing the valve head to wobble about a tiny amount, meaning it doesn't seat cleanly all the time. Carbon builds up in the excess space. Now I know, I am thinking hard about my own car which has one sticky valve. It has a sloppy piston in No. 5 (skirt has been expanded)  and sticky valve in No. 6, plus the occasional odd noise from the timing chain area and the BE bearings aren't wonderful. Maybe it is overhaul time.

Edited by Spinneyhill (see edit history)

Share this post


Link to post
Share on other sites

The ethanol in the gas acts as a good cleaner for the fuel system if you drive a couple of tanks of gas through the car. 

 

Alcohol is a good solvent for varnish.

Edited by Larry Schramm (see edit history)

Share this post


Link to post
Share on other sites

I have and have seen and dealt with several instances of it. Not a good situation.

Never start an engine on varnished fuel!!!!

Edited by c49er (see edit history)

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...